225 runs rough and shakes

[elwilliams13]

My 1991 evinrude 225 runs perfect at 5500 rpm with a 14 1/4 x 18 ss prop, but at lower rpm(2000-2500) it begins to sound as if it were missing and has a little shake to it. I run 87 octane and use a water remover every third tank, pennzoil marine oil and correct plugs. Could this be the midrange jets on my carbs plugging up or a leak somewhere in the idle circuit? Any help is appreciated.

 

[Hooty]

Re: 225 runs rough and shakes

Could be. Next time you're running in that range and it starts to skip or miss, give the priming switch a short, quick bump and see if it picks up just a second before it floods. <br /><br />c/6<br />Hooty

 

[Solittle]

Re: 225 runs rough and shakes

Suggest that you check your ignition with a spark testor. Your description fits a cylinder dropping out at WOT. If you find spark a bit weak on one cylinder It might be time to replace the plug wires (can switch around to confirm).

 

[elwilliams13]

Re: 225 runs rough and shakes

How far should the spark be able to jump on the cylinders?

 

[seahorse5]

Re: 225 runs rough and shakes

In the service manual there is an explanation of throttle linkage synchronization. That is the relationship between throttle opening and the spark advance.<br /><br />If it is out of adjustment, the motor will run very rough in the transition range where the carburetors are switching from the low speed circuits to the mid and high speed range.